dj plastic fork

99 ml 320
ok i've got a problem that seems to be spreading
first the brake light goes out (centre)
then the air conditioning knobs (all three) go out
and then to make matters worse
the horn goes out
i've already checked ALL the related fuses and relays
everything there works
i've also tried hooking the horn directly to the baterry and the horn is working fine
so i know the problem is somewhere in between
the brake lights and airconditoning knobs could be burnt out bulbs, im thinking they are
but the horn is wierd because when i press the horn, a clicking noise comes from the relay that is assigned to the horn.
the relay itself is working fine though
so what can be the problem?
this is pretty urgent, because the alarm system is pointless if the horn doesnt work
TIA